Definition 1.2 (Jensen–Shannon divergence [1]})
The Jensen–Shannon divergence or JS-divergence \(D_{JS}:\mathcal {P}\times \mathcal {P}\rightarrow [0,\infty )\)  is defined between two Radon–Nikodym densities \(p\)  and \(q\)  of \(\mu \) -absolutely continuous probability measures by
\(D_{JS}[p\Vert q] &\frac{1}{2}\Biggl (D_{KL}\Big [p\Big \Vert \frac{p+q}{2}\Big ] + D_{KL}\Big [q\Big \Vert \frac{p+q}{2}\Big ]\Biggr ) \\&= \frac{1}{2}\int _\mathcal {X}\Biggl (p\ln \frac{2p}{p+q} + q\ln \frac{2q}{p+q}\Biggr ) d\mu \\&= D_{JS}[q\Vert  p].\) 

